Cultivators of this type are used for maintaining landscaped ground surfaces, including turf. In this sense the term “turf” refers to grass and other material which is specifically grown for playing sport and used for example to form golf course greens, sporting fields and bowling greens. Cultivators are frequently used on these types or surfaces for repeatedly penetrating the ground surface, forming a plurality of holes so that the ground surface is aerated, to improve growth of the grass or other material and enhance the condition of the surface for playing purposes.
In conducting this type of aeration of turf surfaces, the neatness of the edges of the hole made by the cultivator can significantly affect the overall result. For example in the case of golfing or bowling greens and the like where the vegetation is short, a hole with rough edges or too large a hole can cause spot erosion, resulting in an undesirable dimple in the ground surface. This effect is aggravated when the forward movement of a cultivator differs from the speed of the hole-making tool over the ground surface, causing the hole-making tool to “break” the ground surface. Often this problem is encountered in cultivators powered by a link to a prime mover (such as a tractor), where difficulties in synchronising the speed of the hole making tool with the speed of the prime mover, arises, for example due to different gear ratios between the driving wheels of the tractor and the power link.
One known cultivator described in Australian Patent Application 73500/87 has a structure mounted on ground engaging wheels with tool support means mounted on the frame so that the tool support means is moveable relative to the structure. A cultivating tool, usually a tine or series of tines is mounted on a flat plate so that the tine(s) are relatively vertical to the plate. The plate is mounted on the tool support means via a pair of link arms so that the plate (and vertical tines) freely pivots relative to the tool support means.
As the cultivator moves forward along the ground surface (via a prime mover), the fly wheel drives one end of the tool support member in a circular path. This causes the other end of the tool support means to move in a reciprocating motion so that the cultivating tool is repeatedly forced into the ground surface. This cycle of reciprocating motion of repeated penetrations by the cultivation tool is used to produce holes and is generally referred to as an aeration time cycle. The horizontal plate freely pivots about the tool support means via link arms, so that the cultivating tool tends to be substantially vertical despite the rotation of the fly wheel during the aeration time cycle. Accordingly, the cultivating tool is kept substantially vertical for entry and withdrawal from the ground surface as the link arms will pivot to compensate for forward motion of the cultivating device. That is, at each part of the cycle in which the tool is withdrawn from the ground surface, the freely pivoting link arms positions the cultivation tool in a substantially vertical position for the next cycle of penetration into the ground. This means that fairly neat holes are produced in the ground through this flywheel arrangement.
While this cultivator achieves fairly neat holes in ground surfaces such as turf, the free pivoting arrangement of the cultivation tool restricts the depth of holes that can be produced. This is at least partly the result of the above described cultivator not being suitable for scaling up in size. If this cultivating device is directly scaled up to a larger machine to provide deeper holes, the number of holes in a given surface area would reduce because the distance between holes formed by the cultivating tool would also be scaled upward. The distance between these holes would increase because the necessary scaling up of the size of the flywheel is to increase vertical travel of the cultivating tool. While it has been proposed to use a plate of increased area to cover this increased distance (using a larger number of tines per plate), such plates are unwieldy and awkward as well as requiring greatly increased power to effect penetration of the larger number of tines.